Inner tube



R. F. WILSON ETAL INNER TUBE Filed March 12, 1937 April 1, 1941.

Ron- 1- A W INVENTORS IA sorv ATTORNEY Patented Apr. 1, 1941 man was mum r. Wilson and Willard L. Klingman, Akron, Ohio, minors to The Firestone Tire I:

Rubber of Ohio Company, Akron, .Ohio, a corporation Application March 12, 1937, Serial No. 130,528

4 Claims.

This invention relates to inner tubes such as are used in pneumatic tire casings, and more especially it relates to inner tubes that are designed to close or seal a puncture or blow-out in the -tire casing, and to prevent the escape of more than a minor portion of the air therefrom.

it completely. Chamber l3 and chamber It are interconnected by a small passage II that ex- The chief objects of the invention are to provide an improved inner tube of the character mentioned; to provide safety and convenience in the operation of motor vehicles: and to provide an inner tube comprising a puncture-sealing element that normally is out of engagement with the tire casing and hence not subject to the flexing of the latter, whereby heating and consequent deterioration of the said sealing element is avoided. Other objects will be manifest as the specification proceeds.

Of the accompanying drawing:

Figure l is a fragmentary sectional perspective view of a tire casing, and the improved inner tube therein in fully inflated condition; and

Figure 2 is a transverse sectional view of the structure shown in Figure 1 showing the condition of the tire and tube after a blow-out has occurred.

Referring to the drawing, lilis an annular metal tire rim of the drop-center type, and H is a tire casing of usual construction thereon, the tread portion of the tire being shown relatively thin as in the case of well worn tires. The improved inner tube is mounted interiorly of the tire casing.

Said inner tube consists of two concentric com partments l3, ll of which the latter compart- -ment is disposed about the outer periphery of the inner compartment I3 and is considerably smaller than the latter. The inner compartment is formed within an annular elastic tube ii that is of smaller transverse area than tubes normally provided for the particular tire, said tube being provided on its inner periphery with the usual valve stem It for inflation purposes. The outer compartment I4 is formed by an annular elastic rubber wall l'l that is mounted upon the outer periphery of the tube l5 and has its respective lateral margins united to the sidewalls of said tube in the region of-the bead portions of the tire ll. Interiorly of the compartment [4 is a layer of soft cellular sponge rubber l8 that is adhesively secured to the outer face of the tube l5 and extends transversely thereof from thejuncture of wall ll on one side of the tube to a similar point on the opposite side of the tube. The thickness of the sponge rubber layer It is substantial, but is not'enough to fill the chamber tends through the wall of tube It and through sponge layer l8, near one margin of the latter,

the tube It being reinforced about the inner end of said passage by means of a stifl rubber grommet 20 that is vulcanized in place.

The arrangement is such that when the improved inner tube is mounted in a tire II and .inflated, some of the air entering compartment I! will pass therefrom through passage II and enter compartment M, with the result that the pressure in the two compartments is equalized. and sponge rubber layer I8 will be disposed in spaced relation to the wall II, the latter being in engagement with the inner surface of the tire as is most clearly shown in Figure 1. Thus the flexing of the tire incidental to its use is not transmitted to the sponge layer I8, nor is there any friction between said sponge layer and the tube wall ll. The arrangement prevents heating iliftzhe layer 18 and results in longer life of the a er.

The action of the improved inner tube in the event of a blow-out is shown in Figure 2. The rupture of the wall II, from puncture or blowout of the tire casing l I, results in the immediate deflation of tube chamber It, thus creating a pressure differential in chambers l4 and I: that causes the latter to expand and thus to distend the sponge layer [8 throughout its entire area so that a portion thereof is forced into the opening in the tire casing to close and seal the same. Thereafter there is little or no loss of air from the tube since the pressure of the layer 18 against wall I! also effects the closing of the delivery end of passage IS, the latter being positioned at take place while the vehicle is moving at high a point that is relatively remote from the regions of the tire where punctures and blow-outs usually occur. Experience has shown that in inner tubes of the character described initially inflated to 35 pounds pressure, there is a residual pressure of about 20 pounds after the outer chamber It has been deflated. This pressure is s'uflicient to prevent rim-cutting of the tire, and to prevent accidents such as frequently occur when blow-outs speed. f Modification may be'resorted to without departing from the spirit of the invention or the scope of the appended claims.

What is claimed is:

1. An inner tube for pneumatic tires, said inner tube comprising two annular, concentric,-inflatable compartments, of which one compartment is disposed radially outwardly oi the other, a layer oi cellular sponse rubber in the outermost compartment adhered to the inner wall oi the latter and normally spaced from the outer wall thereoi, and means for utilizing the diflerential pressure existing in said compartments when the outer compartment is deflated to expand the inner compartment and thereby to iorce the sponge rubber layer against said outer wall.

2. An inner tube of the character described comprising two annular, concentric compartments oi which one compartment is disposed about the outer periphery of the other, a layer of soft cellular rubber in the outermost compartment extending from one side thereof to the other and adhered to the inner wall thereof in spaced relation to the outer wall, means ior admitting air to the innermost of said compartments, and an air passage extending from said inner compartment to said outer compartment, said passage extending through the intervening tubewall and cellular rubber layer, and being oi relatively small size and so positioned that upon deflation oi the outermost compartment said passage will be sealed by contact 01 the cellular rubber with the wall of the outer compartment as the result of expansion oi the inner compartment due to difl'erential pressure, hei'ore.there is any substantial loss oi air from said inner compartment.

3. A combination as deflned in claim 2 in which the air passage is disposed relatively near One lateral margin of the cellular rubber layer.

4. A fluid pressure retaining device ior pneumatic tires, said device comprising two annular, concentric, inflatable compartments, oi which one compartment extends radially outwardly of the other, a distensible wall separating the two 1 ROBERT 1''. WILSON. WILLARD L. KLINGMAN. 

